Multistrand powder charge

ABSTRACT

A multistrand powder charge consists of a bundle of powder strands fixed by one of their ends on a support. The charge is characterized in that there is provision, in the very heart of the bundle and in at least one region between the support and the free end of the powder strands, of internal bracing means that extend crosswise with reference to the powder strands, designed to hold the said powder strands between them in such a way that each strand is separated from at least one adjacent strand, to allow a gaseous flow between the said powder strands during combustion of the charge.

Elite States atent Mercier et al.

[ 51 Aug. 12, 1975 MULTISTRAND POWDER CHARGE Inventors: Jacques Mercier, Satory; Bernard Lancon, St. Etienne, both of France 3,613,597 10/1971 Warren .l 102 100 FOREIGN PATENTS OR APPLICATIONS 548,930 7/1956 Belgium 102 100 Primary Examiner-Samuel Feinberg Attorney, Agent, or FirmLarson, Taylor & Hinds 5 7] ABSTRACT A multistrand powder charge consists of a bundle of powder strands fixed by one of their ends on a support. The charge is characterized in that there is provision, in the very heart of the bundle and in at least one region between the support and the free end of the powder strands, of internal bracing means that extend crosswise with reference to the powder strands, designed to hold the said powder strands between them in such a way that each strand is separated from at least one adjacent strand, to allow a gaseous flow between the said powder strands during combustion of the charge.

PATENTED AUBI 21975 SHEU MULTISTRAND POWDER CHARGE FIELD OF THE INVENTION The invention relates to multistrand powder charges, i,e., powder charges that comprise an elongated bundle of powder elements called powder strandsf fixed by one of their ends on a support.

BACKGROUND AND SUMMARY OF THE INVENTION Depending upon the nature of the powder, the combustion of such charges can be effected without intervention of any other product (the powder then contain ing both the combustible material and the kindling material) or with intervention of another product in the fluid state (generally containing the kindling material, the powder then containing the combustible material).

The invention applies more especially, because this is the case in which its application appears to offer most interest, to powder charges whose combustion is effected without intervention of another product, the initiation of the reaction being provoked by an igniting device. Such powder charges can be utilized especially for rocket propulsion.

The implanting of the powder strands in the support should be such that the holding of the strands of powder is ensured during the passive life of the charge as well as during its active life.

In its passive life, the powder strands must present sufficient resistance in the course of the various manipulations of the charge (especially of the rocket equipped with a propulsion device that uses a powder charge of this kind). It is especially necessary that if there be shocks in the course of these manipulations, there will be no rupture of the powder strands constituting the charge.

In the active life, ignition of the powder strands causes a considerable gaseous flow whose dynamic effect tends to separate the strands. It must be avoided that, at the moment of ignition, this gaseous flow could cause a sudden separation of the powder strands, risking rupture of some of them, which would be harmful to the regularity of combustion and in some cases entail deterioration of the downstream part of the propulsion device that uses such a powder charge.

To alleviate the above mentioned disadvantages, it has been proposed to hold the powder strands tightly, one against the other, by means of an elastic strap surrounding the totality of the strands at the outside. However, this solution has turned out to be rather unsatisfactory because the combustion of the powder charge is irregular and there is bursting of the bundle of powder strands.

The invention relates to a multistrand powder charge in which the strands of powder are mutually held, both during their passive life and during their active life, such that combustion in the heart of the charge is effected evenly, without bursting of the bundle of powder strands.

The multistrand powder charge of the invention comprises a bundle of powder strands fixed by one of their ends on a support. It is characterized in that there is provided in the very heart of the bundle, in at least one region located between the support and the free ends of the powder strands, means for internal bracing that extend crosswise with reference to the powder strands, arranged to hold the powder strands in such a way that each strand is separated from at least one adjacent strand, to allow gaseous flow between the said powder strands in combustion of the charge.

Aside from this main arrangement, the invention comprises certain other dispositions that are preferably used at the same time, and that will be discussed more explicitly below.

The invention may in any case be well understood by means of the following description as well as the attached drawings, which description and drawings relate to preferred modes of embodiment of the invention, not of course being of any limiting character whatsoever.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 of these drawings is a schematic section of a rocket with a propulsion device designed on the basis of a powder charge in conformity with a first embodiment of the invention.

FIG. 2 is an enlarged section along IIII of FIG. 1.

FIG. 3 shows, by a section analogous to that of FIG. 2, a second embodiment of the invention.

FIG. 4 is a view in perspective, showing a third embodiment of the invention.

FIG. 5 is an end view of a powder charge designed according to a fourth embodiment of the invention.

FIG. 6 is a view in section of a powder charge designed according to a fifth embodiment of the invention.

FIG. 7 finally is a partial developed view of the powder charge of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The rocket shown in FIG. I is equipped with a powder propulsion device designated in general by reference numeral 1. This propulsion device is based in its design on a multistrand powder charge comprising a bundle of powder strands 2, disposed in parallel and fixed by one of their ends on a support 3 which has the form of a plate. In FIGS. 6 and 7, which will be discussed further hereinafter, a multistrand powder charge is shown which comprises a bundle of powder strands disposed radially and fixed by one of their ends on the inner face 30 of a support 3, which is cylindrical.

According to the invention, internal bracing means 4 are provided in the very heart of the bundle of powder strands 2, in at least one region situated between support 3 and the free end of the said powder strands 2. These bracing means 4 extend crosswise with reference to the powder strands 2, and are arranged to hold powder strands 2 between them in such a way that each strand is separated from at least one adjacent strand, to allow a gaseous flow between said powder strands 2 in combustion of the charge. It will be understood then that the powder strands are held with respect to each other, this arrangement imparting to the powder charge excellent resistance to shock and vibration. Moreover, the arrangement of the said bracing means 4 allows regular burning of the powder strands over the whole of their surfaces at the moment of ignition, the combustion being readily propagated across the said bracing means 4.

The fact that the strands of powder 2 are separated at least from an adjacent strand allows the gaseous flow that commences at the moment of ignition to flow satisfactorily between the said powder strands 2 which are thus practically not shifted by the dynamic effect of this flow. At the very most the powder strands 2 undergo an extremely small shift, to come into a position of equilibrium.

Preferably the bracing means 4 are located in one or more regions near the free end of powder strands 2.

When the powder strands 2 are implanted parallel. or substantially parallel, according to a disposition with concentric circular layers (as illustrated in FIG. 2), the bracing means 4 may be constituted by a plurality of closed concentric ties 5a, 5b, 5c, etc., which each surround a circular layer of powder strands 2.

For a like implantation of powder strands 2 (FIG. 3) bracing means 4 may also be constituted by a single tie 6 that successively surrounds the circular layers of powder strands 2, passing from one layer to the other between any two adjacent powder strands 2. The outer circular layer of powder strands 2 may be held by the said single tie 6 or by an independent closed external tie 7.

It should be pointed out that the tie or ties constituting these bracing means 4 may have elastic properties, or on the contrary they may be practically inextensible.

If reference is made to the embodiment illustrated in FIG. 3, it is to be seen that the external circular layer of powder strands 2 may be held by a single tie 6 if the said tie has elastic properties. On the other hand, there will be recourse to the independent outer tie 7 if the single tie 6 is not elastic, said independent external tie 7 then itself being elastic.

Insofar as the single tie 6 is concerned, it is advantageous to provide means of fixation of its two extremities on a powder charge structure. As shown in FIG. 3, one of its ends may be fixed on or about a powder strand 2 disposed at the center, and the other end may be fixed on or about a powder strand 2 that belongs to the outer layer.

According to the embodiment of the invention illustrated in FIG. 4, which is suitable for various types of implantation of powder strands 2, bracing means 4 may be constituted by a grid 8 comprising, on the one hand, bearings for powder strands 2 and, on the other hand, apertures which may exist between the grid and the powder strands, or in the structure. of the grid itself. The said grid 8 may be constituted by two networks of offset or staggered elements 80 and 8b, the two said networks being oriented crosswise with reference to each other and being joined at their intersecting points by braces 9, oriented parallel to powder strands 2. The said powder strands 2 are then captured in the squares defined by the two said networks 80 and 8b. This shifted disposition of the two networks 8a and 8b promotes the passage of the gaseous flow between powder strands 2, while ensuring effective holding of the said powder strands 2.

According to a modification which is not illustrated, it would be possible to constitute the bracing means 4 by several interconnected, offset networks, the interconnection being effected by axial braces.

When the powder strands 2 are implanted according to an arrangement forming lines and columns (FIG. 5), the bracing means 4 may comprise two ties 10a and 10b situated in different planes, one of the said ties, tie 10a, separating and surrounding the lines of powder strands 2, whereas the other tie, tie 10b, separates and surrounds the columns of powder strands 2.

According to a modification of the invention, it would be possible to provide more than two ties, which would be situated in different planes and which would alternately separate the lines and the columns of powder strands 2. As indicated in connection with FIG. 4, this shifting of ties 10a and 10b facilitates the gaseous flow in the heart of the network of powder strands 2.

According to the embodiment illustrated in FIGS. 6 and 7, bracing means 4 are a grid type. The said grid 8 is constituted by axially longitudinal elements and circular elements Sdjoined to each other at their points of intersection.

Insofar as the constitution of bracing means 4 as described above is concerned, various materials may be used, but it is advantageous to constitute the said bracing means of plastic or of an elastomer, because of the elastic properties that are found in these materials, and because of possibilities of molding, if bracing means of the grid type are to be used.

Generally the material constituting bracing means 4 is a consumable material (plastic, elastomer) which is destroyed in the course of moments after initiation of the combustion. The powder strands 2 are nonetheless held between them during ignition and establishing of the gaseous flow, i.e. during the period in which the relative position and the holding of powder strands 2 have to be ensured to obtain satisfactory propagation of the ignition front and to avoid ruptures in powder strands 2. However, provision can be made for bracing means 4 of a material capable of resisting combustion conditions, the powder strands 2 then remaining braced for a longer time.

In any case, whatever the embodiment adopted, there is a powder charge presenting advantages deriving from the following features: resistance to vibration and shock in the passive life of the powder charge; stability and relative positioning of the powder strands at the moment of ignition; simplicity of design; possibility of adaptation for existing multistrand powder charges.

As is evident, and as it derives moreover from what has been said above, the invention is in no way limited to those modes of application and embodiment that have been more particularly described: it includes on the contrary any modifications.

We claim:

1. Multistrand powder charge comprising a bundle of elongate rod-like individual powder strands fixed by one of their ends on a support so as to extendtherefrom to their oppositely located free ends; internal bracing means in the heart of the bundle and in at least one region between the support and the free end of the powder strands, extending crosswise relative to and between the powder strands, for separating and holding the said powder strands fixedly relative to each other and such that each strand is separated from at least one adjacent strand by said internal bracing means, to allow a gaseous flow between the said powder strands during the combustion of the charge and maintain the bundle as an integral unit, the separations between adjacent strands constituting open gas flow paths over at least the major part of the lengths of said strands.

2. Multistrand powder charge as in claim 1, in which the powder strands are generally parallel and arranged in concentric circular layers, and wherein the internal bracing means are constituted by a plurality of concen- I tric closed ties each surrounding a circular layer of powder strands.

3. Multistrand powder charge as in claim 1, in which the powder strands are generally parallel and arranged in concentric circular layers, and wherein the internal bracing means are constituted by a single tie that successively surrounds the circular layers of powder strands, passing from one layer to another between two adjacent powder strands of the same layer, the external circular layer of powder strands being held by the said single tie.

4. Multistrand powder charge as in claim 1, in which the powder strands are generally parallel and arranged in concentric circular layers, and wherein the internal bracing means are constituted by a single tie that successively surrounds the circular layers of powder strands, passing from one layer to another between two adjacent powder strands of the same layer, the external layer of powder strands being held by an independent closed external tie.

5. Multistrand powder charge as in claim 1, in which the powder strands are generally parallel and arranged in lines and columns, and wherein the internal bracing means are constituted by two ties situated in different planes, one of the said ties substantially surrounding and separating the lines of powder strands, whereas the other tie substantially surrounds and separates the columns of powder strands.

6. Multistrand powder charge as in claim 1, wherein the internal bracing means are constituted by a grid that comprises on the one hand bearings for the powder strands and on the other hand spaces between the grid and the powder strands.

7. Multistrand powder charge as in claim 6, wherein the grid comprises at least two offset networks of spaced elements, the two said networks being oriented crosswise with reference to each other and joined by crosspieces at their intersections.

8. Multistrand powder charge as in claim 1, wherein the powder strands are fixed by one of their ends on the inner face of a cylindrical support, and wherein the bracing means are constituted by a grid that comprises longitudinal elements and circular elements joined at their intersections.

9. Multistrand powder charge as in claim 1 wherein the internal bracing means have elastic properties.

10. Multistrand powder charge as in claim 1 wherein the internal bracing means are constituted by a consumable material that is destroyed in the moments following initiation of combustion of the powder charge.

11. Missile or rocket equipped with a powder propulsion device comprising a multistrand powder charge as claimed in claim 1.

12. Multistrand powder charge as claimed in claim 1 wherein the powder strands are generally parallel.

l3. Multistrand powder charge as claimed in claim 12 wherein said powder strands are arranged in generally concentric circular layers as viewed longitudinally, and wherein the internal bracing means comprise tie means surrounding adjacent circular layers so as to separate adjacent layers and maintain the bundle as an in- 

1. Multistrand powder charge comprising a bundle of elongate rod-like individual powder strands fixed by one of their ends on a support so as to extend therefrom to their oppositely located free ends; internal bracing means in the heart of the bundle and in at least one region between the support and the free end of the powder strands, extending crosswise relative to and between the powder strands, for separating and holding the said powder strands fixedly relative to each other and such that each strand is separated from at least one adjacent strand by said internal bracing means, to allow a gaseous flow between the said powder strands during the combustion of the charge and maintain the bundle as an integral unit, the separations between adjacent strands constituting open gas flow paths over at least the major part of the lengths of said strands.
 2. Multistrand powder charge as in claim 1, in which the powder strands are generally parallel and arranged in concentric circular layers, and wherein the internal bracing means are constituted by a plurality of concentric closed ties each surrounding a circular layer of powder strands.
 3. Multistrand powder charge as in claim 1, in which the powder strands are generally parallel and arranged in concentric circular layers, and wherein the internal bracing means are constituted by a single tie that successively surrounds the circular layers of powder strands, passing from one layer to another between two adjacent powder strands of the same layer, the external circular layer of powder strands being held by the said single tie.
 4. Multistrand powder charge as in claim 1, in which the powder strands are generally parallel and arranged in concentric circular layers, and wherein the internal bracing means are constituted by a single tie that successively surrounds the circular layers of powder strands, passing from one layer to another between two adjacent powder strands of the same layer, the external layer of powder strands being held by an independent closed external tie.
 5. Multistrand powder charge as in claim 1, in which the powder strands are generally parallel and arranged in lines and columns, and wherein the internal bracing means are constituted by two ties situated in different planes, one of the said ties substantially surrounding and separating the lines of powder strands, whereas the other tie substantially surrounds and separates the columns of powder strands.
 6. Multistrand powder charge as in claim 1, wherein the internal bracing means are constituted by a grid that comprises on the one hand bearings for the powder strands and on the other hand spaces between the grid and the powder strands.
 7. Multistrand powder charge as in claim 6, wherein the grid comprises at least two offset networks of spaced elements, the two said networks being oriented crosswise with reference to each other and joined by crosspieces at their intersections.
 8. Multistrand powder charge as in claim 1, wherein the powder strands are fixed by one of their ends on the inner face of a cylindrical support, and wherein the bracing means are constituted by a grid that comprises longitudinal elements and circular elements joined at their intersections.
 9. Multistrand powder charge as in claim 1 wherein the internal bracing means have elastic properties.
 10. Multistrand powder charge as in claim 1 wherein the internal bracing means are constituted by a consumable material that is destroyed in the moments following initiation of combustion of the powder charge.
 11. Missile or rocket equipped with a powder propulsion device comprising a multistrand powder charge as claimed in claim
 1. 12. Multistrand powder charge as claimed in claim 1 wherein the powder strands are generally parallel.
 13. Multistrand powder charge as claimed in claim 12 wherein said powder strands are arranged in generally concentric circular layers as viewed longitudinally, and wherein the internal bracing means comprise tie means surrounding adjacent circular layers so as to separate adjacent layers and maintain the bundle as an integral unit. 